“Today was the first day it has solidly gone up over the $11.50,” Hunt said after trading closed Wednesday.

The 1.3 million units “is a good amount for them.” According to Standard & Poor’s, an average of 800,000 Cedar Fair units were traded per day during the past year.

A portfolio manager at a firm that holds Cedar Fair stock said Wednesday he also noticed the trading activity.

He assumed it was based on speculation that other companies might be interested in acquiring Cedar Fair.

The name mentioned most often is the Blackstone Group, which, like Apollo, is a private equity company. Late last year, the Blackstone Group acquired Busch Entertainment Corp., which operates 10 entertainment parks in the United States, including three SeaWorld parks, two Busch Gardens parks and other family entertainment parks.

Heather Lucania, a spokeswoman for the Blackstone Group, said the company has no comment.

“Unfortunately, I can’t give you any guidance on that at all,” she said.

Stacy Frole, a spokeswoman for Cedar Fair, said the company has no comment on Wednesday’s unit price.

“We wouldn’t be able to comment on speculation in the marketplace,” she said.

Frole noted, however, that 1.3 million units represents about 2 percent of the outstanding shares and said there have been similar volumes of trade in recent weeks.

“We were over a million units on Monday as well, as well as the week before Christmas, too,” she said.